primary property Null safety
Whether this is the primary scroll view associated with the parent PrimaryScrollController.
When this is true, the scroll view is scrollable even if it does not have sufficient content to actually scroll. Otherwise, by default the user can only scroll the view if it has sufficient content. See physics.
Also when true, the scroll view is used for default ScrollActions. If a ScrollAction is not handled by an otherwise focused part of the application, the ScrollAction will be evaluated using this scroll view, for example, when executing Shortcuts key events like page up and down.
On iOS, this also identifies the scroll view that will scroll to top in response to a tap in the status bar.
final bool primary;